A study examined 12 preschool children's early use of "who,""what," and "which" questions in spontaneous speech. Results indicated that children began to ask object questions before they asked subject questions, and acquired argument questions before adjunct questions. It was suggested that the two results could reflect the syntactic structure of the questions or the learning mechanism of the children, but that the results were most consistent with the hypothesis that children are able to theta-govern traces before they are able to antecedent-govern traces. (MSE)